You picked out a vinyl plank you love, the boxes are stacked in the hallway, and now someone has told you the real work happens under the floor. They are right. Most vinyl failures, from planks that click apart to seams that telegraph every bump, trace back to the subfloor rather than the product. Knowing how to prep floors for vinyl is the difference between a floor that looks good for years and one that complains by its first winter.
The short version is that a vinyl floor is only as good as the surface under it, and that surface has to be flat, clean, dry and solid. This guide follows the order a real job unfolds: what comes out, what can stay, how to level and patch, how to check moisture, and where homeowners in older Chicago buildings most often get tripped up.
What Does a Subfloor Need Before Vinyl Goes Down?
A subfloor needs to be flat, clean, dry and solid, and it has to meet the requirements in your vinyl manufacturer’s installation instructions. Those instructions set the flatness tolerance, the moisture limits and the approved underlayments, and they are what a warranty claim gets measured against.
Thin vinyl follows the surface it sits on. A ridge, a screw head, or a patch of leftover adhesive will eventually show through, and a soft spot will stress the locking joints of a floating plank.
Step 1: Clear the Room and Remove What Is in the Way
Empty the room, then take off baseboards, shoe molding, and thresholds. Undercut door casings with a flush-cut saw so planks can slide underneath. Carpet and pad always come out, along with every staple and tack strip.
In older Chicago two-flats, greystones and vintage condos, expect several generations of flooring, old adhesive, and boards that have shifted over a century of heating seasons. If your layers might include mid-century resilient flooring, read the safety section below before you pick up a scraper.
Can Vinyl Go Over Your Existing Floor?
Sometimes, but only if the existing floor is flat, firmly fastened, and approved by the vinyl manufacturer as a substrate. Use this table as a starting point and confirm against your product’s instructions.
| Existing floor | Can it stay? | What prep it usually needs |
|---|---|---|
| Hardwood | Often, if flat, tight and dry | Re-fasten loose boards, fix cupped or high areas, fill gaps, and add an approved underlayment if required |
| Old vinyl or linoleum | Sometimes, if one well-bonded layer | Confirm it is fully adhered, remove wax and residue, and skim coat texture so it will not telegraph |
| Ceramic or stone tile | Often, if tiles are solid | Replace loose tiles, fill grout lines with a suitable patching compound, and level lippage |
| Concrete slab | Yes, once tested | Moisture test, grind high spots, patch cracks, fill low areas, and vacuum thoroughly |
| Plywood or OSB subfloor | Yes, if sound | Re-screw to the joists, replace damaged panels, and add a smooth underlayment panel if the product calls for one |
If the layer underneath moves, crumbles or holds moisture, it goes. Our post on signs your subfloor needs repair before installing new flooring covers the warning signs, such as soft spots, squeaks, and staining, that should stop a job before it starts.
Safety First: Old Resilient Flooring and Adhesives
If your home is older, treat old tile, sheet flooring, and the adhesive beneath it as suspect until a qualified professional says otherwise. The EPA lists vinyl floor tiles, the backing on vinyl sheet flooring and flooring adhesives among the materials where asbestos may be found, and notes that fibers can be released when materials are disturbed during repair and remodeling.
The EPA’s guidance on protecting your family from asbestos exposure says not to saw, sand, scrape or drill into asbestos-containing materials. It also advises against taking samples yourself and points to trained, accredited professionals for inspection, sampling, repair, and removal.
In practice, that means no dry scraping of old adhesive, no sanding to rough it up, and no ripping out cracked tile because it looks rough. If something might contain asbestos, stop, leave it undisturbed and get it assessed. Rules for testing, removal, and disposal vary between Chicago and the suburbs, so ask the professional what applies at your address.
Step 2: Get the Floor Flat
Flatness is where most rushed jobs cut corners. Manufacturers publish a flatness tolerance, usually an allowable gap under a straightedge over a set distance, and it differs by product and installation method. We will not quote a number here because yours may not match it. Find it in the installation instructions and treat it as the standard to hit.
Lay a long straightedge on the floor in several directions and look for daylight underneath. Mark high spots in one color and low spots in another, then work in this order:
- Remove proud nail heads and screws, or drive them below the surface.
- Sand or grind high spots and ridges, but never sand material you suspect contains asbestos.
- Fill low areas, cracks and gaps with a patching or leveling compound made for your substrate.
- Let everything cure fully, then run the straightedge again.
Follow the label on the compound for primers and cure times. A floor that looks flat to the eye can still be out of spec, and the vinyl will tell on you within months.
Step 3: Test for Moisture Before You Commit
Moisture is the quiet killer of vinyl floors, and Chicago has plenty of it. Basement slabs sit against damp soil, wet springs raise groundwater, summer humidity moves through foundations, and freeze-thaw cycles open hairline cracks that let water in over the years.
For concrete, many manufacturers require moisture testing before installation. One common method is described in ASTM F2170, which uses in-situ probes to measure relative humidity inside the slab. The standard notes that excess moisture can cause debonding, peaking and finish deterioration, and that results only reflect the slab at the time and places tested.
Your vinyl maker will say which test it accepts and what reading is acceptable, so follow that. If a slab fails, the usual answer is to fix the source, whether grading, gutters, a leaking pipe or a failing sump, and then retest. A manufacturer-approved moisture barrier may be an option for some products, but only if the instructions allow it.
Wood subfloors need attention too, especially over crawlspaces and basements. Look for staining, cupping, soft spots or a musty smell. The EPA’s brief guide to mold, moisture and your home recommends drying wet areas within 24 to 48 hours and keeping indoor humidity under 60 percent. If the source was a past leak, fix the leak and the damaged wood before anything goes on top.
Step 4: Acclimate the Vinyl and Choose an Underlayment
Acclimation means letting flooring sit in the room before installation. Some manufacturers require a set number of hours, some say it is not required, and most specify a room-temperature range during and after installation. Follow your product’s wording, and in winter bring the heat up to normal living temperature first.
Underlayment follows the same logic. Some planks come with attached padding, and adding another layer can void the warranty or weaken the locking system. Others need a separate underlayment for smoothing or sound. In condos and multi-unit buildings, the association may require a specific sound rating, so check the rules before you order. If you’re still deciding between luxury vinyl and laminate, our comparison explains how the two behave.
Step 5: Clean, Then Install With Room to Move
Vacuum the floor, remove dried debris, and vacuum again. A single trapped pebble can create a bump you will feel for years.
Floating vinyl needs an expansion gap around the perimeter, and the manufacturer sets the size. Trim covers the gap, so there is no reason to skip it.
Plywood or Underlayment Panels Over Old Boards
Many older Chicago homes have plank subfloors with gaps and uneven edges. Vinyl will not bridge gaps or hide board edges, so these floors usually need an underlayment-grade panel fastened over them. Panel type, thickness and fastening pattern should follow the vinyl manufacturer’s rules. Panels also add height, so plan doorway transitions early.
Common Prep Mistakes
Most failures come from the same shortcuts:
- Skipping moisture testing on a basement slab or a floor over a damp crawlspace
- Accepting a floor that is close enough on flatness
- Leaving no expansion gap at walls, cabinets, and pipes
- Laying vinyl over loose boards, soft spots or crumbling patch
- Sanding or scraping old resilient flooring that was never tested
DIY or Professional?
A confident homeowner can handle carpet removal, baseboards, cleaning, and light patching. Hand off the jobs where mistakes are expensive or hidden: moisture testing and remediation, leveling a badly out-of-flat floor, replacing damaged subfloor, and anything involving suspect resilient flooring. When you interview contractors, ask who tests moisture, how they check flatness, and which manufacturer instructions they follow.
On our Marshfield St. kitchen and flooring renovation in Lakeview, we ran the kitchen and floor as a single scope, which avoids the join line where new cabinetry meets an older floor. For a broader look at what we handle, start with our flooring services page.
Frequently Asked Questions
How flat does a floor need to be for vinyl plank?
It depends on the product. Each manufacturer publishes its own flatness tolerance in the installation instructions, and that figure is what a warranty claim is judged against. Check yours before buying patching compound.
Can I install vinyl plank over old vinyl flooring?
Sometimes. A single layer of well-bonded, clean, smooth vinyl may be acceptable if the manufacturer allows it. If it is curling, heavily textured or more than one layer, it usually has to come out or be skimmed. If it could contain asbestos, do not sand or scrape it.
Do I need a moisture test for a basement floor?
In most cases, yes. Many manufacturers require a documented test on concrete, and a Chicago basement slab sees groundwater, humidity and freeze-thaw movement. Ask your installer which method they use and what reading your manufacturer accepts.
How long should vinyl flooring acclimate?
As long as your product’s instructions say. Some require a set period in the room and some say none is needed, but most want the space at normal living temperature before, during and after installation.
Is it safe to remove old vinyl tile myself?
Not if there is any chance it contains asbestos, which may be present in tile and adhesive in older homes. The EPA recommends against sanding, scraping or sampling it yourself.
Conclusion
Knowing how to prep floors for vinyl comes down to patience with the unglamorous steps: take out what does not belong, treat old resilient flooring with caution, get the surface flat, prove it is dry, and follow the manufacturer’s instructions for everything else. Do that and the vinyl itself is the easy part.
If your floor has more history than you expected, or you would rather not guess about moisture and flatness, tell us about your floor and timeline and we can talk through what the subfloor needs before any material is ordered.